enforce primary key to exist in another multi colum primary key - sql

Question

I have two tables. First table has multi columns as the primary key and the second table has one column primary key. Data has be entered first in Table1 FieldPlacement where FieldPlacementNum will be generated then enter a record in Table2 where the FieldPlacementNum has to exist in Table1.
Currently has one to many relationship but I want the reverse the relationship of tables and SQL does not let me do it. thanks
Table 1
CREATE TABLE [dbo].[FieldPlacement]
(
[ID] [varchar](10) NOT NULL,
[Year] [varchar](10) NOT NULL,
[Term] [varchar](10) NOT NULL,
[PlacementNum] [int] IDENTITY(1,1) NOT NULL,
[Email] [varchar](70) NULL,
CONSTRAINT [PK_FieldPlacement]
PRIMARY KEY CLUSTERED ([ID] ASC, [Year] ASC, [Term] ASC, [PlacementNum] ASC)
WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF,
IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON,
ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
SET ANSI_PADDING OFF
GO
ALTER TABLE [dbo].[FieldPlacement] WITH CHECK
ADD CONSTRAINT [FK_FieldPlacement_FieldPlacementEval1]
FOREIGN KEY([PlacementNum])
REFERENCES [dbo].[FieldPlacementEval] ([PlacementNum])
GO
ALTER TABLE [dbo].[FieldPlacement]
CHECK CONSTRAINT [FK_FieldPlacement_FieldPlacementEval1]
GO
Table 2
CREATE TABLE [dbo].[FieldPlacementEval]
(
[PlacementNum] [int] NOT NULL,
[StudentLastName] [varchar](50) NULL,
[StudentFirstName] [varchar](50) NULL,
[TeacherLastName] [varchar](50) NULL,
[TeacherFirstName] [varchar](50) NULL,
CONSTRAINT [PK_FieldPlacementEval]
PRIMARY KEY CLUSTERED ([PlacementNum] ASC)
WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF,
IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON,
ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

Answer 1

Since FieldPlacement.PlacementNum is an IDENTITY, which is NOT NULL and unique, you could also make this your PK, and then just create a unique index on those four columns that currently make up the PK (to ensure their uniqueness).
From your FieldPlacementEval just reference the PlacementNum.
The additional benefit here would be a smaller, more efficient clustering key on your FieldPlacement table (since it's only 1 column instead of 4 - and skips all those variable length columns which are really bad for a clustering key)